A light emitting diode, or “LED,” is well-known in the field of electronics. LEDs are found in all kinds of devices. Among other things, they form the numbers on digital clocks, transmit information from remote controls, light up watches and indicate when an appliance is activated. Alternatively, they can form images on a television screen or illuminate a traffic light. Basically, LEDs function like tiny light bulbs that fit easily into an electrical circuit. Unlike ordinary incandescent bulbs, they do not have a filament but are illuminated solely by the movement of electrons in a semiconductor material.
While all LEDs release light, most do not do it very effectively. In an ordinary diode, the semiconductor material itself ends up absorbing a lot of the light energy. LEDs are specially constructed to release a large number of photons outward. Additionally, they are commonly housed in a plastic bulb or lens that concentrates and directs the light in a particular direction. The main advantage of an LED is energy efficiency. LEDs generate very little heat, relatively to a conventional light bulb. A much higher percentage of the electrical power supplied is directly converted to light. Yet the advantages of this energy efficiency are lost if the light generated is not properly focused and directed in the directions desired.
Many of the lens devices fitted for use with an LED are not capable of directing light in a uniform manner across a range of viewing angles. It is often necessary, especially with electronics and devices using electronics, such as circuit boards, to have light emitting devices be viewable from a range of angles. Most light focusing devices and lenses used with LEDs do not create a source of light that is viewable at constant intensity across the entire range of possible viewing angles. The light emitted is not omnidirectional but has varying intensity or luminance from different viewing angles, such as the top versus the side. Accordingly, it is desirable to provide a method and apparatus that provides for uniform luminance emitted by an LED when viewed from any viewing angle.
Furthermore, many devices employ multi-color LEDs, or clusters of monochromatic LEDs having varying colors, to be able to generate any color within the visible light spectrum. The shape of the LED lens generally does not provide for uniform mixing of the various colors of light emitted by the LED. Nor is the color uniform when viewed from different viewing angles about the LED lens. Therefore, it is desirable to provide a method and apparatus that provides for uniform color mixing and chromaticity for light emitted by an LED when viewed from any viewing angle around the LED.